ORIGINAL_ARTICLE
Nanotechnology and Neuroscience Convergence: A Novel Tool for Neurotransmitters Monitoring
Since neurotransmitters significantly influence the brain activity, our understanding of the human brain will remain imperfect until all aspects relating to them become clear. One of the key challenges in neuroscience researches and therapies is elucidating the mechanisms by which the neurotransmitter release take place and is regulated in quantity and in time. Despite the enormous number of studies carried out to illuminate this function, efficient methods for momentary detection and visualizing these tiny neurochemicals have not been developed yet. Recent advances in nanomaterials have launched a new class of fluorescent labels by conjugating quantum dots (QDs) with biomolecules. Cadmium-based QDs have been by far the most developed in bioimaging; however, their doubtful future owing to high toxicity has turned researchers᾽ attention to more recently ternary nontoxic compounds, CuInS2. In this article a novel application of CuInS2 nanoparticles in neuroscience has been proposed. Accordingly, a newly developed synthesis method have been exploited applying refluxed procedure. The structure and surface analysis taken by TEM and FTIR analyses showed that the resulting nanocrystals have sizes ranging from 1.6 to 3.2 nm while their surface is functionalized with MPA capping ligands. Optical properties of CuInS2, demonstrating broad absorption and narrow emission spectra, 250 nm and 150 nm, respectively, with PL peak of 656 nm and FWHM 49 nm, have also been revealed by spectroscopy. All confirm that QDs are very appropriate for neurotransmitter detection in a small synaptic cleft. It is also suggested that the minimum concentration of [Cu]/[ MPA] required for complete surface coverage is 1:11.
https://www.ije.ir/article_72872_113e59a595e39be92185527bec015c70.pdf
2017-02-01
152
161
Neurotransmitter
synaptic transmission
bioconjugating
bioimaging
CuInS2 QDs
Nanoparticle
Detection
monitoring
photo
luminesence
Reza
Khanbabaie
rezakhan@uottawa.ca
1
Physics, Babol Noshirvani University of Technology
AUTHOR
mahzad
mirzaei
mahzad.mirzaei@yahoo.com
2
AUTHOR
Mohsen
Jahanshahi
mjahan@nit.ac.ir
3
Chemical Engineering, Noshirvani University of Technology, Babol
AUTHOR
ORIGINAL_ARTICLE
Shear Capacity of Reinforced Concrete Flat Slabs Made with High-strength Concrete: A Numerical Study of the Effect of Size, Location, and Shape of the Opening (TECHNICAL NOTE)
Nowadays, concrete with strength higher than 50 MPa is utilized due to the ever increasing need for higher strength and prolonged healing properties. Despite the widespread use of high-strength concrete, only a few research projects have been conducted on the punching shear strength of high-strength concrete slabs. Reinforced concrete flat slabs are widely employed in structural systems. The location of the slab-column connection is the most sensitive part of the flat slab. The present study investigates the effect of existance of opening in reinforced concrete flat slab in two groups of slab, a group with HSC concrete and the other with NSC concrete. To this end, a few examples of flat slabs with different positions, shapes, and dimensions of the opening with normal-strength concrete and, the slabs with the same geometry but high-strength concrete are compared so as to review the effect of high-strength concrete on the slabs with different openings. The results of this research show that the high-strength concrete improves the shear capacity of the slabs and leads to transferring higher forces in slab-column connection. Furthermore, the dimensions, shape, and position of the opening is effective on the percentage of load increase and ultimate deflection of samples.
https://www.ije.ir/article_72873_3cb94ed97c1723c736a58d0dedbb0a62.pdf
2017-02-01
162
171
reinforced concrete flat slab
opening
Numerical method
high
strength concrete
shear capacity
Sara
Ilbegyan
sara.ibn92@gmail.com
1
Civil Engineering, cDeylaman Institute of Higher Educationon
AUTHOR
M.M.
Ranjbar
ranjbar@guilan.ac.ir
2
Civil Engineering, Univercity of Guilan
AUTHOR
Seyed Mohammad
Abdollahi
sm.abdolahi71@gmail.com
3
Civil Engineering, Univercity of Guilan
AUTHOR
ORIGINAL_ARTICLE
A Novel Image Structural Similarity Index Considering Image Content Detectability Using Maximally Stable Extremal Region Descriptor
The image content detectability and image structure preservation are closely related concepts with undeniable role in image quality assessment. However, the most attention of image quality studies has been paid to image structure evaluation, few of them focused on image content detectability. Examining the image structure was firstly introduced and assessed in Structural SIMilarity (SSIM) measure, in which, the definition of image structure is constrained to the intensity covariance between the reference and test images. Indeed, this measure discerns the luminance changes in the pixels of the reference and test images, by employing the low-level statistical features. But this minimal definition of image structure does not cover the issue of image content detectability. In this study, we found that the status of image region smoothness can reflect its structural content. So, we proposed a novel smoothness measure based on the maximally stable extremal regions (MSER) descriptor. Subsequently, we proposed a novel image structural similarity measure, in which the fidelity of image region smoothness is also taken into account. Experimental results on five popular benchmark image databases, include A57, LIVE, CSIQ, TID2008 and TID2013, are provided, which confirm that the proposed approach has a reasonable prediction performance compared to the state-of-the-art image quality metrics.
https://www.ije.ir/article_72874_980b439180757390445e431d61a702c0.pdf
2017-02-01
172
181
Image quality assessment
Image smoothness measure
Maximally stable extremal regions
Content detectability
Hamid
Hassanpour
h_hassanpour@yahoo.com
1
AUTHOR
Mohammad Hossein
Khosravi
mohokhosravi@yahoo.com
2
Electrical and Computer Engineering, University of Birjand
AUTHOR
ORIGINAL_ARTICLE
High Fuzzy Utility Based Frequent Patterns Mining Approach for Mobile Web Services Sequences
Nowadays high fuzzy utility based pattern mining is an emerging topic in data mining. It refers to discover all patterns having a high utility meeting a user-specified minimum high utility threshold. It comprises extracting patterns which are highly accessed in mobile web service sequences. Different from the traditional fuzzy approach, high fuzzy utility mining considers not only counts of mobile web service accessed in a sequence but additionally their preference value while mobile web services sequences are accessed. In this paper, I introduce a new approach, namely HFUBPM (High Fuzzy Utility Based Patterns Mining) for high fuzzy utility patterns extraction from mobile web services accessed sequences. The proposed approach uses a fuzzy minimum operator to extract highly interesting patterns from web service accessed sequences. In this proposed approach, downward closure property in fuzzy sets is handled by an efficient upper bound model. This model improves the efficiency of mining way. At last, the experiments have been performed on both synthetic and real datasets, which show that the proposed approach has good performances in terms of execution and search space.
https://www.ije.ir/article_72875_41a19381680b4c7ca3ac1b5021847434.pdf
2017-02-01
182
191
Mobile web service
Fuzzy mining
Utility mining
High fuzzy utility patters
Mobile web service sequence
krishna
mohbey
kmohbey@gmail.com
1
Computer Science, Central University of Rajasthan
AUTHOR
ORIGINAL_ARTICLE
Improving Linearity of CMOS Variable-gain Amplifier Using Third-order Intermodulation Cancellation Mechanism and Intermodulation Distortion Sinking Techniques
This paper presents an improved linearity variable-gain amplifier (VGA) in 0.18-µm CMOS technology. The linearity improvement is resulted from employing a new combinational technique, which utilizes third-order-intermodulation (IM3) cancellation mechanism using second-order-intermodulation (IM2) injection, and intermodulation distortion (IMD) sinking techniques. The proposed VGA gain cell consists of a variable-gain attenuator followed by a differential cascode amplifier as a fixed-gain stage. The continuous gain control mechanism in the first stage occurs by varying the gate voltage of an nMOS transistor. Our proposed linearization technique is applied to the fixed gain cascode amplifier of the second stage. To examine the linearity of the proposed circuit, a nonlinear analysis of the cascode amplifier based on Taylor series has been performed. The simulation results show that after linearization, the third-order input intercept point (IIP3) of the whole VGA has been improved about +18 dB at the gain of 15.4 dB. The VGA has a voltage gain varying from -7.5 to 19.5 dB and a bandwidth of 830 MHz to 845 MHz. Morever, the circuit dissipates 4.65 mW to 9.35 mW from a 1.8 V single supply over the entire gain range.
https://www.ije.ir/article_72876_6d6f183f64ed8fa5f725da9c4010ec9b.pdf
2017-02-01
192
198
variable
gain amplifier
(IM3) Distortion cancellation
linearity improvment
third
order input intercept point (IIP3)
Gholamreza
Ardeshir
g.ardeshir@nit.ac.ir
1
Elect & Computer Engineering, Babol Nooshirvani University of Technology
AUTHOR
Dariush
Razmjooei
dariush.razmjooei@gmail.com
2
Communications and Electronics, shiraz university
AUTHOR
mohammadreza
asemani
mr.asemani69@yahoo.com
3
electrical and computer engineering, babol university of technology
AUTHOR
ORIGINAL_ARTICLE
Comparative Analysis of Image Denoising Methods Based on Wavelet Transform and Threshold Functions
There are many unavoidable noise interferences in image acquisition and transmission. To make it better for subsequent processing, the noise in the image should be removed in advance. There are many kinds of image noises, mainly including salt and pepper noise and Gaussian noise. This paper focuses on the research of the Gaussian noise removal. It introduces many wavelet threshold denoising algorithms which include global threshold denoising, Maxmin threshold denoising, and BayesShrink threshold denoising. We emphatically analyze the strengths and weaknesses of different denoising methods based on different threshold functions. Besides, we make a comparative analysis for these denoising methods. The experimental result shows that the wavelet images denoising algorithm based on Gaussian mixture model is better than that of the global threshold and Maxmin threshold, and also slightly better than BayesShrink threshold.
https://www.ije.ir/article_72877_eefc92e4170f350f820acd2347a4851b.pdf
2017-02-01
199
206
Image Denoising
wavelet transform
threshold function
gaussian mixture model (GMM)
Lin
Lin
sdwhwdy@163.com
1
, Shandong University
AUTHOR
Liangang
Feng
liangangfeng@163.com
2
Department of Information Engineering, Weihai Vocational College
AUTHOR
ORIGINAL_ARTICLE
Constrained Model Predictive Control of Low-power Industrial Gas Turbine
Nowadays, extensive research has been conducted for gas turbine engines control due to growing importance of gas turbine engines for different industries and the need to design a suitable control system for a gas turbine as the heart of the industry. In order to design gas turbine control system, various control variables can be used, but in the meantime, fuel flow inserting into combustion chamber will be a sufficient alternative due to its remarkable influence in compassion with all parameters of engine functionality such as rotors turn, compressor pressure ratio, specific fuel consumption and inlet turbine temperature. It should be noted that some of these parameters must be operated in a specific operation range. Therefore, we must adopt an appropriate control system to hold parameters within acceptable region. On the other hand, gas turbine encompasses complex, nonlinear and time-variant behavior such that mentioned parameters are constantly changing with variations of operating conditions. In this paper, a closed loop Model Predictive Control (MPC) controller has been designed which can be executed based on optimization process.
https://www.ije.ir/article_72878_459bee2c3e8eefd73dcd3a87433c1cab.pdf
2017-02-01
207
214
Low
power industrial gas turbine
Model Predictive Control (MPC)
constrained MPC
close loop optimization
Ali
Akbar Ghafouri Rokn Abadi
alighafouri12@yahoo.com
1
Information Technology Group, K. N.Toosi University of Technology
AUTHOR
ORIGINAL_ARTICLE
Improvement of Navigation Accuracy using Tightly Coupled Kalman Filter
In this paper, a mechanism is designed for integration of inertial navigation system information (INS) and global positioning system information (GPS). In this type of system a series of mathematical and filtering algorithms with Tightly Coupled techniques with several objectives such as application of integrated navigation algorithms, precise calculation of flying object position, speed and attitudes at any moment. Obviously, GPS speed information will contribute to make better estimates of the state in addition to location information. Typically, Kalman filter provides optimal method for states estimation and also creates possibility of combining several measurements to acquiesce a united estimate of system status.Tightly Coupled Kalman filter is a novel and applicable approach to effectively track path with high accuracy especially when four satellites are not available or satellite system stops along the route. Indeed, an important advantage of integration with Tightly Coupled filtration is related to application of software system rather than hardware which somehow reduces hardware complexity and also other advantages of sensors integration is associated with application of all benefits of various sensors as well as covering their individual imperfections in order to increase navigation accuracy. Generally, in integration systems exact GPS observations are used to estimate and INS errors modification by Kalman filter. It is expected that an integrated system with high-precision provides an accurate estimation of all unknowns’ parameters and states through kalman filter. Simulations executed for integrated navigation system demonstrate that a flying object could sufficiently compensate errors resulting from modeling of inertial navigation that grows integrally over time and also impressively inhibit flying object deviation respect to condition that only GPS location information are available.
https://www.ije.ir/article_72879_82078746ec4eb4fe01a9d79c731b15c6.pdf
2017-02-01
215
223
Kalman Filter
Inertial Navigation System
global positioning systems
integrated INS/GPS
Tightly Coupled
Ali
Valizadeh
a_vali237@yahoo.com
1
AUTHOR
Hojatollah
Hamidi
h_hamidi@kntu.ac.ir
2
, K. N.Toosi University of Technology
AUTHOR
ORIGINAL_ARTICLE
Solving a New Multi-objective Unrelated Parallel Machines Scheduling Problem by Hybrid Teaching-learning Based Optimization
This paper considers a scheduling problem of a set of independent jobs on unrelated parallel machines (UPMs) that minimizesthe maximum completion time (i.e., makespan or ), maximum earliness ( ), and maximum tardiness ( ) simultaneously. Jobs have non-identical due dates, sequence-dependent setup times and machine-dependentprocessing times. A multi-objective mixed-integer linear programming (MILP) is considered then solved with the ε-constraint method in small-sized problems.The related results are compared with the results obtained by meta-heuristic algorithms.Furthermore, an effectivehybrid multi-objective teaching–learningbased optimization (HMOTLBO) algorithm is proposed, whose performance is compared with a non-dominated sorting genetic algorithm (NSGA-II) fortest problems generated at random. The associated results show that the proposed HMOTLBO outperformsthe NSGA-II in terms of different metrics.
https://www.ije.ir/article_72880_fb404fe60084150a810e6ae2fa7a3d0e.pdf
2017-02-01
224
233
Teaching–learning based optimization
Unrelated Parallel Machines
makespan
Tardiness
Earliness
Bahman
Naderi
bahman.naderi@aut.ac.ir
1
industrial engineering department, kharazmi university
AUTHOR
Reza
Tavakkoli-Moghaddam
tavakoli@ut.ac.ir
2
Industrial Engineering, University of Tehran
AUTHOR
Azam
Sadati
industrial7781@yahoo.com
3
Department of Industrial Engineering, Islamic Azad University
AUTHOR
Mohammad
Mohammadi
mohammadi@khu.ac.ir
4
Department of Industrial Engineering, Kharazmi University
AUTHOR
ORIGINAL_ARTICLE
A Time Dependent Pollution Routing Problem in Multi-graph
This paper considers a time dependent(the travel time is not constant throughout the day) pollution routing problem (TDPRP), which aids the decision makers in minimizing travel time, toll cost and emitted pollution cost. In complexity of urban areas most of the time one point is accessible from another with more than one edge. In contrast to previous TDPRP models, which are designed with only one edge between two nodes, the existence of more than one edge between two nodes is allowed in our modeling. Thus we develop a new model that is called time dependent pollution routing problem in multi-graph (TDPRPM). Since the problem is NP-hard, a tabu search (TS) algorithm is developed to solve it. Finally, computational results of tabu search procedure and its comparison to exact solution are presented.
https://www.ije.ir/article_72881_3fb81b62813f8c6a5467a8afe7911ba9.pdf
2017-02-01
234
242
Time – dependent
pollution routing problem
multi
Graph
Tabu Search
Amirhosein
Patoghi
amirhpa.ah@gmail.com
1
Industrial Engineering, K. N. Toosi University of Technology
AUTHOR
Zohreh
Shakeri
arezoo_shakeri@yahoo.com
2
Industrial Engineering, K. N. Toosi University of Technology
AUTHOR
Mostafa
Setak
setak@kntu.ac.ir
3
, K. N. Toosi University of Technology
AUTHOR
ORIGINAL_ARTICLE
Unreliable Server Mx/G/1 Queue with Loss-delay, Balking and Second Optional Service
This investigation deals with MX/G/1 queueing model with setup, bulk- arrival, loss-delay and balking. The provision of second optional service apart from essential service by an unreliable server is taken into consideration. We assume that the delay customers join the queue when server is busy whereas loss customers depart from the system. After receiving the essential service, the customers may opt for the optional service with some probability or may leave the system. The server is unreliable and hence may breakdown in both essential and optional service cases and requires a setup time before being repaired. The service during essential service, setup times and repair times for both cases are general distributed while the service time during optional service is exponential. Using the supplementary variable technique, the equations governing the model are constructed. The steady state queue size distribution is then obtained using Laplace transform and probability generating functions. The numerical results for various performance indices have been obtained and illustrated graphically.
https://www.ije.ir/article_72882_dd7d884db6abce4a3ac35ba429fcab10.pdf
2017-02-01
243
252
Bulk Queue
Loss and delay
Essential service
Optional service
Supplementary variables
Queue Size
Pankaj
Sharma
sharma_ibspankaj@rediffmail.com
1
Mathematics, Noida International University, India
AUTHOR
ORIGINAL_ARTICLE
Determining the Sample size for Estimation of the CCC-R Control Chart Parameters Based on Estimation Costs
In today's highly competitive industrial environment due to fast technology development, quality practitioners will to detect out-of-control situations and take actions whenever is necessary as soon as possible. Accordingly, new statistical procedures have been enhanced incessantly both to handle high yield processes along with looking for methods of minimizing all quality cost. CCC-r chart, the extended method of CCC charts, is commonly applied when nonconforming items are rarely observed. Since the values of the parameters used for the design of the charts' control parameters are usually unknown in practice, the practitioners need to estimate them by using an in-control retrospective sample. It has been shown that parameter estimation affects the control charts' properties severely. This study develops a model based on estimation costs and Average Number of Inspected Items for CCC-r chart when nonconforming fraction is unknown. The unknown parameters estimated based on different values of sample sizes and sensitivity analysis of is performed.
https://www.ije.ir/article_72883_5a83af6a30bbb553d6303200e5742b32.pdf
2017-02-01
253
260
Statistical process control
high yield process
CCC
r control charts
parameter estimation
Average Number Inspected
Economic design
vida
golbafian
v.golbafian.90@gmail.com
1
, Yazd university
AUTHOR
Mohammad Saber
Fallah Nezhad
fallahnezhad@yazd.ac.ir
2
Industerial Engineering, Yazd Univarsity
AUTHOR
ORIGINAL_ARTICLE
Critical Path Method for Flexible Job Shop Scheduling Problem with Preemption
This paper addressed a Flexible Job shop Scheduling Problem (FJSP) with the objective of minimization of maximum completion time (Cmax) which job splitting or lot streaming is allowed. Lot streaming is an important technique that has been used widely to reduce completion time of a production system. Due to the complexity of the problem; exact optimization techniques such as branch and bound algorithm will lose their efficiency at medium and large dimensions. Thus, metaheuristic techniques are good options in order to obtain high quality solutions within a reasonable computational time. In this study, firstly, the considered problems are solved in both permitted and not permitted of lot streaming by means of memetic algorithm and then the obtained solutions will be improved by using the critical path method heuristic. The numerical results indicate the high efficiency of the memetic algorithm in comparison with the previous methods; in addition, adding preemption and using allowable idle machines have led to a considerable improvement in the objective function.
https://www.ije.ir/article_72884_ca3686222f82eafd22caf938d8073671.pdf
2017-02-01
261
269
Memetic algorithm
Flexible Job shop Scheduling Problem (FJSP)
preemption
Critical Path
Babak
Yousefi Yegane
babak.yaganeh@uok.ac.ir
1
, Islamic Azad University, Malayer Branch, Malayer,
AUTHOR
Narges
Khanlarzade
n.khanlarzade@modares.ac.ir
2
Industrial Engineering, Tarbiat Modares University
AUTHOR
Isa
Nakhai Kamalabadi
i.nakhai@uok.ac.ir
3
Industrial Engineering, University of Kurdistan
AUTHOR
ORIGINAL_ARTICLE
Monitoring Financial Processes with ARMA-GARCH Model Based on Shewhart Control Chart (Case Study: Tehran Stock Exchange)
Financial surveillance is an interesting area after financial crisis in recent years. In this subject, important financial indices are monitored using control charts. Control chart is a powerful instrument for detecting assignable causes which is considerably developed in industrial and service environments. In this paper, a monitoring procedure based on Shewhart control chart is proposed to monitor financial processes modeled with ARMA-GARCH time series structure. The effect of parameter estimation and power of change detection are evaluated through simulation studies. Then, the proposed method is applied to monitor Tehran Stock Exchange price index (TEPIX) as the main motivation of this research. The obtained results show the ability of the proposed method in comparison with market analysis.
https://www.ije.ir/article_72885_05aeb5dc10ae2ff516bc383af4e55bfb.pdf
2017-02-01
270
280
Financial surveillance
ARMA
GARCH model
Shewhart control chart
parameter estimation
Tehran Stock Exchange
Hojatollah
Sadeghi
sadeqi@yazd.ac.ir
1
Department of Business Management, Yazd University
AUTHOR
Mohammad Saleh
Owlia
owliams@gmail.com
2
Department of Industrial Engineering, Yazd University
AUTHOR
Mohammad Hadi
Doroudyan
doroudyan@stu.yazd.ac.ir
3
Industrial Engineering Department, Yazd University
AUTHOR
Amirhossein
Amiri
amiri@shahed.ac.ir
4
Industrial Engineering, Shahed University
AUTHOR
ORIGINAL_ARTICLE
Experimental Investigation on the Effect of Partially Metal Foam inside the Absorber of Parabolic Trough Solar Collector
In the present work the efficiency of a solar parabolic trough has been investigated experimentality. parabolic trough solar collector constitute a proven source of thermal energy for industrial process heat and power genaration. The impact of using the partially porous media in the absorber on the efficiency of PTC (parabolic trough collector) has been investigated. The porosity of copper foam is 0.9 and the pore density is 30 PPI (pores per inch). The experiments were performed in different volume flow rates from 0.5 to 1.5 Lit/min and the standard of ASHRAE 93 was used to test the solar collector’s performance. Results illustrate that using metal foam in the absorber has a positive impact on the collector efficiency and increases the pressure drop in the absorber. When absorber filled with metal foam the overall loss coefficient UL decreases 45% and it causes to increase efficiency because less energy is lost.
https://www.ije.ir/article_72886_57a25340d9839cc9517f42d13a9065d6.pdf
2017-02-01
281
287
solar parabolic trough collector
metal foam
ASHRAE 93 standard
Thermal efficiency
Thermal conductivity
Milad
Tajik Jamal-Abad
miladtajik6@gmail.com
1
Department of Renewable Energy, Material and Energy Research Center(MERC)
AUTHOR
ORIGINAL_ARTICLE
Mechanical Properties and Microstructural Evolution of Ta/TaNx Double Layer Thin Films Deposited by Magnetron Sputtering
Crystalline tantalum thin films of about 500nm thickness were deposited on AISI 316L stainless steel substrate using magnetron sputtering. To investigate the nano-mechanical properties of tantalum films, deposition was performed at two temperatures (25°C and 200°C) on TaNx intermediate layer with different N2/Ar flow rate ratio from 0 to 30%. Nano-indentation was performed to obtain the mechanical properties of the films including hardness, Young’s modulus and plasticity free of substrate influence. Cross sectional FESEM was performed to measure the thickness of films. To evaluate the results, the grain size and crystallographic structure of the films was obtained, using atomic force microscopy (AFM) and X-Ray diffraction (XRD) respectively. It was found that, increasing sputtering temperature up to 200°C leads to slight decrease in hardness and Young’s modulus, and small increase in plasticity due to grain growth without any phase transformation. Whereas, using TaNx interlayer promoted formation of cubic-tantalum with higher plasticity and lower hardness in comparison to tetragonal structure, so it can makes tantalum film an applicable product for mechanically protecting.
https://www.ije.ir/article_72887_602addafb8117a702e8358c19156c91a.pdf
2017-02-01
288
293
Nano
indentation
Tantalum
Thin film
Grain Size
Phase Characterization
Gholamhosein
Akbari
ghh.akbari@gmail.com
1
Department of Material Science and Engineering, Shahid Bahonar University of Kerman
AUTHOR
Morteza
Nikravesh
nikravesh.mse@gmail.com
2
Department of Material Science and Engineering, Shahid Bahonar University of Kerman
AUTHOR
A.
Poladi
a.poladi@yahoo.com
3
Materials Science and Engineering, Semnan University
AUTHOR
ORIGINAL_ARTICLE
An Investigation on the Effects of Gas Pressure Drop in Heat Exchangers on Dynamics of a Free Piston Stirling Engine
This paper is devoted to study the effects of pressure drop in heat exchangers on the dynamics of a free piston Stirling engine. First, the dynamic equations governing the pistons as well as the gas pressure equations for hot and cold spaces of the engine are extracted. Then, by substituting the obtained pressure equations into the dynamic relationships the final nonlinear dynamic equations governing the free piston Stirling engine are acquired. Next, effects of the gas pressure drop in heat exchangers on maximum strokes of the pistons and their velocities and accelerations are investigated. Furthermore, influences of pressure drop increase in the heat exchangers on maximum and minimum gas volume and pressure in both hot and cold spaces are evaluated. Finally, the trend of variations of work and power corresponding to the increase of pressure drop in the heat exchangers are studied. Based on the obtained results of this paper, the assumption of uniform pressure distribution in the engine cylinder (as used in the Schmidt theory) causes some errors in predicting the dynamic behavior of the free piston hot-air engines. Besides, the increase of pressure drop in the heat exchangers results in deteriorating the dynamic performance of the engine.
https://www.ije.ir/article_72888_c2999863236368b249ccebcb20083a48.pdf
2017-02-01
294
302
Free piston Stirling engine
Dynamics
Pressure drop
hot and cold spaces
Shahryar
Zare
s.zare@sutech.ac.ir
1
Mechanical and Aerospace Engineering, Shiraz University of Technology
AUTHOR
Omid
Aghajanzadeh
aghajanzadeh_omid@mech.sharif.ir
2
Mechanical Engineering, Sharif University of Technology
AUTHOR
ORIGINAL_ARTICLE
Performance Evaluation of Magnetorheological Damper Valve Configurations Using Finite Element Method
The main purpose of this paper is to study various configurations of a magnetorheological (MR) damper valve and to evaluate their performance indices typically dynamic range, valve ratio, inductive time constant and pressure drop. It is known that these performance indices (PI) of the damper depend upon the magnetic circuit design of the valve. Hence, nine valve configurations are considered for which mathematical models are developed. A finite element model is built to analyze and investigate the PI of a 2-D axi-symmetric MR damper valve. All configurations of the damper valve are simulated within a given range of input current and number of turns of coil, and within this range, damping force, dynamic range, valve ratio, inductive time constant and achieved pressure drop have been evaluated. The simulation results show that the PI of the MR damper are highly dependent on the shapes of valves and hence the valve shape should be selected based on the intended application. The results obtained in this work provide an insight for designers to create application-specific MR dampers.
https://www.ije.ir/article_72889_7451fd32cdac0f0bb6aeca83fa28afd3.pdf
2017-02-01
303
310
Magneto
rheological (MR) damper
damping force
dynamic range
valve ratio
inductive time constant
Pressure drop
Sujatha
Srinivasan
sujsree@iitm.ac.in
1
Mechanical Engineering, Indian Institute of Technology Madras
AUTHOR
Solomon
Kebede
solomonseid@gmail.com
2
Production Engineering, College of Engineering, Defence University
AUTHOR
Sujatha
Chandramohan
sujatha@iitm.ac.in
3
Mechanical Engineering, Indian Institute of Technology Madras
AUTHOR
ORIGINAL_ARTICLE
Free Vibration Analysis of Nonuniform Microbeams Based on Modified Couple Stress Theory: an Analytical Solution
In this study, analytical solution is presented to calculate the free vibration frequencies of nonuniform microbeams. Scale effects are modelled using modified couple stress theory and the microbeam is assumed to be thin while Poisson's ratio effects are also taken into account. Nonuniformity is presented by exponentially varying width among the microbeam while the thickness remains constant. Results are presented for simply-supported, cantilever and clamped boundary conditions. First five natural frequency parameter are calculated for different scale and nonuniformity parameters and effects of each parameter on the results are discussed. Also, to understand the effects of Poisson's ratio, small scale and nonuniformity on the first frequency of the nonuniform microbeam and resonance domain, a comprehensive parametric study is done. This research is important in understanding the dynamic behavior of microbeams and effective designs using variable cross section in this type of microstructures.
https://www.ije.ir/article_72890_626e793a5d1a730fb34d270dfe3fcf79.pdf
2017-02-01
311
320
Modified couple stress theory
microbeam
variable cross section
Free vibration
Analytical Solution
S.
Hosseini Hashemi
shh@iust.ac.ir
1
, Iran University of Science and Technology
AUTHOR
Hossein
Bakhshi Khaniki
bakhshi.khaniki@gmail.com
2
Mechanical Engineering, Iran University of Science and Technology
AUTHOR
ORIGINAL_ARTICLE
A Strain Range Dependent Cyclic Plasticity Model
Hysteresis loop curves are highly important for numerical simulations of materials deformation under cyclic loadings. The models mainly take account of only the tensile half of the stabilized cycle in hysteresis loop for identification of the constants which don’t vary with accumulation of plastic strain and strain range of the hysteresis loop. This approach may be quite erroneous particularly if the mean stress is not small and the effect of isotropic hardening is large. A strain dependent cyclic plasticity model which considers the variation of material constants versus strain range and accumulation of plastic strain has been proposed and experimentally investigated by the authors. In this paper it is proved that their proposed model is accurate for simulating all cycles of the hysteresis loop regardless of the strain range of the test. It is shown in this work that artificial neural network (ANN) model, if designed and trained properly, can be used for interpolating and extrapolating the experimental data. The results of this work are compared with two well-known cyclic plasticity models. The results also indicate that there is a remarkable agreement between the proposed model and ANN within and outside the strain ranges used in the experiments.
https://www.ije.ir/article_72891_463f17664e73a067c3dbe48572f32bcf.pdf
2017-02-01
321
329
Simulation
hysteresis loop
cyclic plasticity model
Neural Network
G. H.
Majzoubi
gh_majzoobi@basu.ac.ir
1
Mechanical Engineering, Buali Sina University of Hamadan
AUTHOR
Ehsan
Khademi
ehsankhademime@gmail.com
2
Robotics, Hamedan University of Technology (HUT)
AUTHOR
N
Bonora
nbonora@unicas.it
3
, Casyino universit
AUTHOR